1. Field of the Invention
The present invention relates to apparatus for supplying measured doses of lubricants to a lubricating line. In particular, the present invention relates to devices for dosing lubricants to a lubricating line wherein the devices of the type having at least one manual throttling element limiting the volume flow of the lubricant into the lubricating line.
2. Description of the Prior Art
Such dosing devices with manual throttling element are used for specific central lubrication tasks in the parallel distribution of lubricant flows depending upon the requirements of the machine manufacturers or operators. The manual adjustability of the manual throttling element is necessary in practice to reduce the volume flow for a specific period of time in the case of cold, highly viscous lubricants and to prevent an overflow of lubricating points in the case of a reflux which is still deficient due to the viscosity. A machine-load-dependent lubricant dosing is adjusted in each case in a relatively simple fashion. Relatively large volume flows up to about 6 1/min. are dosed to the lubricating points in body presses, large transmissions and paper machines.
In the dosing device known from the print sheet No. 01 80.03.86 of Eugen Woerner GmbH & Co., D-6980 Wertheim the flow metering device is an inspection pipe with a floating piston as sensor element, whose position determined by the volume flow is electrically monitored. The boundary values of the volume flow are entered on a scale. An LED display serves for the function control by indicating whether the floating piston has reached or exceeded a previously determined position in the inspection pipe.
The, dosing device according to the publication "Durchflu.beta.messer", 48715 PB1 of the DE LIMON FLUHME GmbH & Co. company, D-4000 Dusseldorf 1 works according to the same principle, an electric switching contact being actuated as a function of the position of the floating body.
These dosing devices work in a strongly viscosity-dependent fashion, i.e. they must be calibrated at a specific lubricant temperature. Static flow metering devices are concerned since the floating body remains immovable under the adjusted volume flow during operation. Several disadvantages result from this. Due to impurities contained in the lubricant and substances deposited e.g. due to the additives under thermal and mechanical load, the inspection pipe becomes clogged. A direct visual control of the position of the floating body is rendered difficult or even impossible after a longer service life. The floating body often remaining immovable for weeks gets caught due to such deposits and delivers then an "erroneous" "okay" message despite a changing volume flow. These impurities change the flow cross-sections near the floating body so that it changes its position and generates a "erroneous" fault signal, although the volume flow is correct or still within an admissible tolerance range or generates an "erroneous" "okay" signal although the volume flow is no longer correct. A serious disadvantage of these static flow metering devices is moreover the incorrect display of the volume flow and the difficult exact calibration. This is also due to the fact that the floating body only indicates whether the nominal volume flow has been reached or not reached or exceeded. In lubricating systems in which such relatively inexpensive throttling dosing devices which are easy to handle are used, this has been put up with so far as being inevitable and it was attempted by means of frequent controls and knocking against the inspection pipe to ensure a proper function and to avoid damages in the lubricating points. Therefore it has become a custom to let supervisors control all dosing devices practically daily although the adjusted volume flow is not changed for weeks or months.
Dynamic flow metering devices are known per se. According to DE-OS 29 43 184 a flow metering cell for a flowing liquid contains a gearwheel or an impeller, whose rotational speed is inductively scanned to detect the actual flow. The wheel may consist of plastic material and be equipped with permanent magnets. This principle is not suited for relatively viscous lubricants. An oval wheel meter serving as flow counter with an electric pulse transmitter on a wheel serves for determining the oil consumption of an oil burner according to DE-OS 35 11 537.